The present invention generally relates to on-board fuel storage and delivery to an engine in a vehicle and, more particularly, relates to vehicle fuel management for controlling fuel storage and delivery to the engine.
Automotive vehicles are typically powered by an internal combustion engine that converts the chemical energy of a fuel (e.g., gasoline) to mechanical energy for driving a powertrain which, in turn, propels the vehicle via road wheels. Additionally, some of the mechanical energy is also converted to electrical energy via an alternator and is stored in a battery and used to power various electrically operated devices. Vehicles are being equipped with increasing numbers of electrically powered devices, all of which consume energy. Thus, it is desirable to enhance the efficiency of the electrically powered devices in order to maximize the overall energy efficiency of the vehicle.
Automotive vehicles employ a fuel storage tank and a fuel delivery system that delivers a controlled amount of fuel from the fuel storage tank to one or more fuel rails having fuel injectors for dispensing the fuel into the internal combustion engine. At the engine, the fuel injectors inject a controlled mixture of the fuel and air into the individual engine cylinders. Many conventional fuel delivery systems typically employ a single speed on/off fuel pump for pumping pressurized fuel from the fuel storage tank to the fuel rail which, in turn, supplies the pressurized fuel to the individual fuel injectors. The fuel pump is powered by an electric motor that is operated such that the motor is either off (de-energized) to provide no pumping action or the motor is on (energized) to pump fuel at a fixed pumping speed. The fuel output from the pump flows through a mechanical regulator that regulates the amount of fuel delivered to the fuel rail at a predetermined pressure. Pumped fuel that is not delivered to the fuel rail is returned to the fuel storage tank via a return path from the mechanical regulator.
Many conventional fuel delivery system fuel pumps are continuously operated at a fixed speed as long as the ignition key is in the on position, regardless of the engine fuel demands. The fuel pump generates an audible noise when energized at the normal fixed speed. This results in a continuous audible noise which can be noticeable to vehicle occupants, particularly when the engine is operated at low engine load demands, e.g., engine idle speed. Continued full speed operation of the fuel pump further consumes electrical energy, which could otherwise be made available elsewhere to enhance the vehicle energy efficiency. Additionally, the return of a large amount of excessive fuel through the regulator to the fuel storage tank may cause heating of the fuel that, in turn, creates unwanted gas vapor, which adds to evaporative emissions, and which then must be vented through a charcoal canister. Reducing the fuel pump speed reduces the vapor, which reduces the emissions to reduce the global warming and ozone depletion potentials caused by the fuel vapors.
Fuel delivery systems have been proposed that employ a variable speed fuel pump electrically controlled to increase and decrease pump speed. One example of a fuel delivery system is disclosed in U.S. Pat. No. 4,926,829, entitled “PRESSURE-RESPONSIVE FUEL DELIVERY SYSTEM.” The fuel delivery system described in the aforementioned patent employs a pressure regulator in a fuel return line, and a pressure sensor for monitoring pressure in the return line. The fuel pump is energized at low or high levels depending on the fuel back-pressure in the return line. Many such fuel delivery systems are generally complex and costly. It is desirable to provide for a fuel delivery system having reduced complexity and cost.
Mounted within the fuel storage tank is a carbon (e.g., charcoal) canister for collecting fuel vapor to reduce evaporated emissions. The vapor collection canister has a fuel vapor vent for venting pressurized gas from within the fuel storage tank, and also has a fuel vapor purge actuator for purging the collected fuel vapor from the vapor collection canister for burning in the engine. The fuel vapor vent and purge actuator are periodically operated in response to command control signals generated by the engine control module. The fuel collection canister is typically periodically purged, without regard to measuring the actual amount of fuel vapors collected therein. During a fuel fill operation, for example, when the fuel storage tank is excessively filled with fuel, the fuel canister may rapidly become saturated, hence requiring a purge operation. The fuel fill tube leading to the fuel tank generally includes a mechanical float valve which shuts off the conventional fuel fill dispensing nozzle upon reaching a predetermined fuel tank pressure. However, it is possible to continue to dispense incremental amounts of fuel in the fuel storage tank, thereby leading to saturation of the vapor collection canister.
The conventional fuel pump motor is generally controlled (on or off) in response to a command signal received from the vehicle engine control module (ECM) (a/k/a, engine control unit) which performs a multitude of vehicle functions generally related to engine operation. The engine control module also controls other devices related to the storage and delivery of fuel to the engine by outputting on/off command signals to various devices to control the individual devices. Conventional fuel delivery systems rely primarily upon the engine control module to control the various fuel storage, delivery, and management functions by controlling such devices on and off, but do not provide for optimal integration of fuel delivery functions.
Accordingly, it is therefore desirable to provide for a fuel management system that overcomes deficiencies of prior known vehicle systems for controlling the fuel storage and delivery of fuel to the engine on the vehicle. In particular, it is desirable to provide for an integrated system of managing fuel storage and delivery within a vehicle. It is also desirable to provide for a cost affordable fuel delivery system that provides enhanced energy efficiency, reduced audible noise, and reduced wiring. It is further desirable to provide for a fuel delivery system that offers enhanced fuel management integration including, but not limited to, fuel tank vent, fuel vapor purge and fuel fill operations.